over

Copyimport { over } from "https://github.gh-proxy.cn/raw.githubusercontent.com/baetheus/fun/main/fn.ts";

A common pattern in optics is to apply an input value to a function at the beginning and the end of a computation. This can (and has) been achieved by the composition of Pair using flow(P.dup, P.map(fn), P.merge). But for performance reasons it's nice to have a straighforward function that achieves the same result.